1. Field of the Invention
The present invention generally relates to light source driving devices, and particularly to a light source driving device with a full-bridge circuit.
2. Description of Related Art
Generally, discharge lamps used in liquid crystal display (LCD) panels, such as Cold Cathode Fluorescent Lamps (CCFLs) or External Electrode Fluorescent Lamps (EEFLs), need to be driven by specific driving circuits. With the size of LCD panels ever increasing with advances in technology, the number of discharge lamps used in the LCD panels correspondingly increases as well. Inevitably, driving circuits, such as transformers, full-bridge circuits, etc, are added.
FIG. 1 is a prior light source driving device 100 with a full-bridge circuit. The light source driving device for driving a power source 14 comprises a power stage circuit 11, a first transformer circuit 12, a second transformer circuit 13, and a feedback control circuit 15. The power source 14 comprises a plurality of lamps. The power stage circuit 11 comprises two full-bridge circuits respectively composing of switches Q11, Q12, QA1, QB1 and Q21, Q22, QA2, QB2, for converting received power signals to AC signals. The first transformer circuit 12 and the second transformer circuit 13 are respectively connected to the two full-bridge circuits for transforming the AC signals to drive the light source 14. The feedback control circuit 15 is electrically connected between the light source 14 and the power stage circuit 11, for controlling the output of the power stage circuit 11 according to feedback current from the light source 14.
In practical applications, the light source 14 has certain load characteristics, where only one of the two full-bridge circuits has a soft-switching function, and operates at a lower temperature. The other full-bridge circuit does not have the soft-switching function, and the operating temperature thereof is relatively higher. The different temperature performances of the two full-bridge circuits shorten the life of the light source driving device. Further, the requirement of eight switches in the two full-bridge circuits is costly.